"The pace of human-induced climate change is accelerating. We need results now, results that curb global greenhouse emissions," Ban said at the opening of high-level talks at the annual U.N. climate conference.

In the two-week session's final days, environment ministers will seek agreement on knotty side issues in coping with global warming, but once more the U.N. climate treaty's 193 parties will fail at Cancun to produce a sweeping deal to slash greenhouse gas emissions and control climate change.

"I am deeply concerned that our efforts so far have been insufficient," the U.N. chief said.

"Nature will not wait while we negotiate. Science warns that the window of opportunity to prevent uncontrolled climate change will soon close."

Activists from Via Campesina, an international movement of peasants, demonstrate Tuesday during the United Nations Climate Change Conference in Cancun, Mexico. (Eduardo Verdugo ~ Associated Press)

Another reminder came from the mountains of South Asia: In a new report, experts said people's lives and livelihoods are at "high risk" as warming melts Himalayan glaciers, sending floods crashing down from overloaded mountain lakes and depriving farmers of steady water sources.

Secondary tools

Despite such evidence of growing effects, and scientists' warnings that temperatures will rise sharply in this century, the world's nations have made little progress over the past decade toward a new global pact on emissions cuts to replace the 1997 Kyoto Protocol. The Republican rebound in Washington promises to delay action even further.

Instead, environment ministers will focus on secondary tools for confronting global warming, laying the groundwork, for example, for a "green fund" of $100 billion a year by 2020.

Financed by richer nations, the fund would support poorer nations in converting to cleaner energy sources and in adapting to a shifting climate that may damage people's health, agriculture and economies in general.

Negotiators also hope to agree on a mechanism giving poorer countries' easier access to the patented green technology of advanced countries, and on pinning down more elements of a complex plan to compensate developing nations for protecting their climate-friendly forests.

Activists protest

Year after year at these U.N. sessions, activists frustrated by their slow pace have rallied in protest. On Tuesday, hundreds marched from downtown Cancun toward the heavily guarded beach resort area where the conference is taking place. About a dozen protesters managed to get inside the conference complex, marching briefly through a meeting hall before being escorted away by security guards.

American action

High-level guidance from the environment ministers may be needed most in the coming days' debates over limited gestures proposed on emissions reductions.

The U.S. has long refused to join the rest of the industrialized world in the Kyoto Protocol, a 1997 add-on to the climate treaty that mandates modest emissions reductions by richer nations, and whose commitments expire in 2012. The U.S. complained Kyoto would hurt its economy and should have mandated actions as well by such emerging economies as China and India.

Last month's election of a Republican majority in the U.S. House of Representatives all but rules out for at least two years U.S. legislation to cap carbon dioxide and other global-warming gases emitted by industry, vehicles and agriculture. Such American action is deemed essential to winning a new global pact on emissions.

China and other poorer, growing nations, for their part, have rejected calls that they submit to Kyoto-style legally binding commitments -- not to reduce emissions, but to cut back on emissions growth. Their first obligation, these governments say, is to lift their people from poverty, and not potentially hobble their economies.

In a nonbinding Copenhagen Accord emerging from last December's climate summit in the Danish capital, the U.S. and other industrial nations announced targets for reducing emissions by 2020, and China and some other developing nations set goals, also voluntary, for cutting back on emissions growth.

That accord was not accepted by all treaty parties. Now many negotiators want to have the voluntary targets "anchored" more formally in a final Cancun document -- but how, with what wording and form of commitment, will be subject to backroom haggling in the coming days.

The glacier report, issued here by the U.N. Environment Program and glacier researchers, said that "since the beginning of the 1980s, the rate of ice loss has increased substantially in many regions, concurrent with an increase in global mean air temperatures."

Glaciers in southern South America and Alaska's coastal mountains have been losing mass faster and for longer than glaciers elsewhere in the world, it said.

The experts said the incidence of "glacial lake outburst floods" has grown over the past 40 years, accounting for some of the 5,000 Asian deaths each year from flash floods. More broadly, the swift depletion of glacial waters may leave tens of thousands of farmers without irrigation water.

"The risk to lives and livelihoods in the fragile Hindu Kush Himalayan region is high and getting higher," said Madhav Karki of the Nepal-based International Center for Integrated Mountain Development.